"[Brett] Murray called the work 'an attempt at humorous satire of political power and patriarchy within the context of other artworks in the exhibition'.

"The painting ignited a storm in South Africa, with the ANC and its political allies calling the painting racist while artists and the Freedom of Expression Institute decried the ruling party's efforts to suppress the work."

As Reuters reports in its story, opinion about the painting is divided along racial lines, but that is complicated by the fact that Murray, who is white, made his name as an artist by criticizing the apartheid government that ruled until 1994.

Today, the debate reached fever pitch, when two men — one white and one black — snuck into the Goodman gallery with two small containers of paint. One of them used a paintbrush to draw two Xes on Zuma's face and penis, and the other smeared black paint across the canvas using his hands. It was all caught on tape.

The National Post reports that the vandalism occurred "as about 400 supporters of the ruling African National Congress (ANC) sang and danced in downtown Johannesburg in support of Zuma."

In an interview with Reuters before the incident, the ANC Secretary General Gwede Mantashe said people had a right to criticize the president but when someone portray his genitals "you are not raising a discussion, you are insulting people."

Gareth van Onselen, a columnist in South Africa, called the vandalism an "absolutely disgraceful act."

"There'll be a temptation to dismiss this as funny," Van Onselen said on Twitter. "It is not. It is profound. South Africa's tolerance was tested and we failed."

The Democratic Alliance, an opposing political party originally formed by anti-apartheid activists in 1959, put out a statement saying that "powerful art cannot be erased."